Which of the porosity logs is most sensitive to the liquid and gas component of

Question

Which of the porosity logs is most sensitive to the liquid and gas component of the rock? Acoustic log Neutron log Density log Sonic log Which of the following is these properties is directly measured by a neutron porosity tool? hydrogen index porosity atomic weight Compressional velocity Which of the following information about the photoelectric effect is true? Provides information about compton-scatering of gamma rays Provides information about the electron density of formations Provides information about the hydrogen concentration of formations Provides information about the absorption of high speed photons Which of the following logs is not affected by the solid (matrix) composition of a rock if the rock is saturated with freshwater Photoelectic index Gamma ray log Spectral gamma ray Self potential

Explanation / Answer

Porosity determines reservoir storage capacity. It is defined as the ratio of void space, commonly called pore volume, to bulk volume and is reported either as a fraction or a percentage. Almost all hydrocarbon reservoirs are composed of sedimentary rocks in which porosity values generally vary from 10 to 40% in sandstones and from 5 to 25% in carbonates

The neutron log mainly measures hydrogen concentration in a formation.

The logging device is a noncontact tool that emits neutrons from a source. Emitted neutrons collide with nuclei of the formation and lose some of their energy. Maximum energy loss occurs when emitted neutrons collide with hydrogen atoms because a neutron and a hydrogen atom have almost the same mass. Therefore, most neutron energy loss occurs in the part of the formation that has the highest hydrogen concentration.

Neutron energy loss can be related to porosity because in porous formations, hydrogen is concentrated in the fluid filling the pores. Reservoirs whose pores are gas filled may have a lower porosity than the same pores filled with oil or water because gas has a lower concentration of hydrogen atoms than either oil or water.

Therefore answer to Q12 is neutron log

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